Phototoxic potential of undispersed and dispersed fresh and weathered Macondo crude oils to Gulf of Mexico Marine Organisms

Abstract

Crude oils contain a mixture of hydrocarbons, including phototoxic polycyclic aromatic hydrocarbons (PAHs) that have the ability to absorb ultraviolet (UV) light. Absorption of UV light by PAHs can substantially increase their toxicity to marine organisms. The objective of the present study was to examine the potential for phototoxicity of fresh and naturally weathered Macondo crude oils alone and in combination with the dispersant Corexit 9500 to mysid shrimp (Americamysis bahia), inland silverside (Menidia beryllina), sheepshead minnow (Cyprinodon variegatus), and Gulf killifish (Fundulus grandis). Acute toxicity tests were conducted using combinations of natural or artificial sunlight and low-energy water-accommodated fractions (WAFs) of fresh and weathered Macondo crude oils collected from the Gulf of Mexico. Studies were also conducted to compare the phototoxicity resulting from natural and artificial sunlight. Fresh Macondo crude oil was more phototoxic than weathered crude oils, both in the presence and in the absence of UV light. Differences in toxicity between fresh and weathered crude oils were likely attributed to lighter-ringed PAHs in fresh crude oils. Phototoxic PAHs were relatively resistant to weathering compared with lighter-ringed PAHs. The addition of Corexit 9500 to crude oil increased toxicity compared with tests with crude oil alone, by increasing phototoxic PAH concentrations in WAFs. Macondo crude oils had the potential to be phototoxic to Gulf of Mexico marine organisms if specific light conditions and PAH concentrations were present during the Deepwater Horizon oil spill. Environ Toxicol Chem 2017;36:2640-2650. © 2017 SETAC.

Photoenhanced Toxicity of Weathered Crude Oil in Sediment and Water to Larval Zebrafish

“…There was less than 10% mortality of zebrafish larvae in the water-only control and the two dispersant-only treatments, including the 100% sunlight exposures, indicating a lack of phototoxicity in the absence of oil. These results are consistent with other studies showing that dispersants alone are not phototoxic to aquatic organisms Alloy et al 2017;Finch et al 2017;Sweet et al 2017). There was 0% survival of fish exposed to 100% solar radiation in the oil WAF high and CEWAF high treatments, which were significantly different from the almost complete survival of larvae exposed to 10% solar radiation (chi-square ≥ 4.5; p-value ≤ 0.03; Fig 1).…”

“…There have been relatively few studies of the photoenhanced toxicity of chemically dispersed oil since the first report by . Recently, studies with fish and invertebrate species native to the Gulf of Mexico have confirmed the phototoxicity of chemically dispersed oil from the Deepwater Horizon spill in laboratory water exposures (Alloy et al 2017;Finch et al 2017;Sweet et al 2017).…”

Predicting phototoxicity of alkylated PAHs, mixtures of PAHs, and water accommodated fractions (WAF) of neat and weathered petroleum with the phototoxic target lipid model

“…For the petroleum phototoxicity assessment, 4 species indigenous to the Gulf of Mexico, including A. bahia , M. beryllina , C. variegatus , and F. grandis were exposed to 3 field‐collected oils. Natural sunlight (Supplemental Data, Worksheet 2, Table WS2‐15 for the full spectrum), solar‐simulated light (Supplemental Data, Worksheet 2, Table WS2‐15 for the full spectrum), and no light exposure studies were conducted with exposure concentrations of 100, 25, and 6.25% WAF . The CTLBBs for A. bahia , M. beryllina , and C. variegatus are from the literature .…”

Phototoxicity Assessments of Field Sites in Barataria Bay, Louisiana, USA, and Heavily Weathered Macondo Crude Oil: 4 Years after the Deepwater Horizon Oil Spill

“…Weathering of oil removes lighter PAH compounds (1-2 rings), while retaining heavier PAHs, some of which are known to be phototoxic (3-5 rings; Riley et al 1980;Barron et al 1999). Several crude oils have been demonstrated to be phototoxic (Cleveland et al 2000; Barron et al 2003) including Macondo crude oil (Alloy et al 2015;Finch et al 2017). Macondo crude oils contain significant concentrations of phototoxic PAHs (Finch et al 2017).…”

“…Several crude oils have been demonstrated to be phototoxic (Cleveland et al 2000; Barron et al 2003) including Macondo crude oil (Alloy et al 2015;Finch et al 2017). Macondo crude oils contain significant concentrations of phototoxic PAHs (Finch et al 2017). Finch et al (2016Finch et al ( , 2017 reported increased toxicity to mysid shrimp, inland silverside, and Pacific and eastern oyster larvae exposed to weathered Macondo crude oil water accommodated fractions (WAFs) in the presence of sunlight.…”